If a word or a construction causes problems and seems too difficult for the moment, make a mental note of it and come back later, when you're ready for it. Which you will be one day in the not too distant future, provided you really want to.

When or if you really need something, you'll find it much easier to remember and use.

Don't be too easily discouraged, look back at what you've already achieved.

And don't set your aims too high. Just high enough to reach without undue effort. Success breeds succeed. And every single tiny bit of progress is still progress. As the Spanish say: "Muchos pocos hacen un mucho." Lots of little somethings eventually make one whopping big something. And that goes for progress as well.